Hello, Using the 10kHz output to lock an OCXO is common practice and seems to give good results. Has anyone tried to use the 1pps output? One? could first make a simple divider to create a 0.5Hz reference with 50% duty cycle, and then use this signal to lock an OCXO. This would also allow the use of other OEM GPS modules that don't have the 10kHz but only the 1pps signal. Of course, as the 0.5Hz signal is much lower in frequency than 10kHz, the short-term stability is pushed more to the OCXO, making the requirements of the OCXO even harder. But maybe the 1pps signal has better stability than the 10kHz signal? Or is this the same since these signals will only influence the long-term stability of the oscillator and have the same accuracy? Any thoughts are highly appreciated. Thanks, Patrick.

Patrick, This has been covered extensively in recent past (this year). A quick look through the archives will tell you more than you bargained for... Didier > -----Original Message----- > From: time-nuts-bounces@febo.com > [mailto:time-nuts-bounces@febo.com] On Behalf Of Patrick Reynaert > Sent: Sunday, December 21, 2008 4:13 PM > To: time-nuts > Subject: [time-nuts] Jupiter modules: 1pps or 10kHz to lock an OCXO ? > > Hello, > > > Using the 10kHz output to lock an OCXO is common practice and > seems to give good results. > > Has anyone tried to use the 1pps output? One? could first > make a simple divider to create a 0.5Hz reference with 50% > duty cycle, and then use this signal to lock an OCXO. This > would also allow the use of other OEM GPS modules that don't > have the 10kHz but only the 1pps signal. > > Of course, as the 0.5Hz signal is much lower in frequency > than 10kHz, the short-term stability is pushed more to the > OCXO, making the requirements of the OCXO even harder. > > But maybe the 1pps signal has better stability than the 10kHz > signal? Or is this the same since these signals will only > influence the long-term stability of the oscillator and have > the same accuracy? > > Any thoughts are highly appreciated. > > Thanks, > Patrick. > > > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com To unsubscribe, > go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.

Patrick, I don't know of an analog approach using the 1 pps divided to 0.5 Hz (for 50% duty cycle) as input to a phase detector. 1 Hz ripple frequency from the phase detector is probably not practical to filter. You would need a low pass filter time constant of at least 1000 seconds and I think capacitors that will work for the long time constant will have poor temperature properties, leading to excess drift. Digital approaches using the 1 pps signal compared to a divided OCXO signal are used by most modern designs. Bob Q. ----- Original Message ----- From: "Patrick Reynaert" <preynaert@yahoo.com> To: "time-nuts" <time-nuts@febo.com> Sent: Sunday, December 21, 2008 2:13 PM Subject: [time-nuts] Jupiter modules: 1pps or 10kHz to lock an OCXO ? > Hello, > > > Using the 10kHz output to lock an OCXO is common practice and seems to > give good results. > > Has anyone tried to use the 1pps output? One? could first make a simple > divider to create a 0.5Hz reference with 50% duty cycle, and then use this > signal to lock an OCXO. This would also allow the use of other OEM GPS > modules that don't have the 10kHz but only the 1pps signal. > > Of course, as the 0.5Hz signal is much lower in frequency than 10kHz, the > short-term stability is pushed more to the OCXO, making the requirements > of the OCXO even harder. > > But maybe the 1pps signal has better stability than the 10kHz signal? Or > is this the same since these signals will only influence the long-term > stability of the oscillator and have the same accuracy? > > Any thoughts are highly appreciated. > > Thanks, > Patrick. > > > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.

I thought of something else. Time to lock can be really long. Say the OCXO can swing +/- 1 ppm, +/- 10 Hz at 10 MHz. The +/- 1 ppm also applies to 0.5 Hz. To swing 180 degrees at 0.5 Hz, assuming the low pass filtered control signal pushes the OCXO the full 1 ppm, will take 1e6 seconds unless you use a circuit similar to what I used to prealign 50 Hz signals in the 100 Hz Motorola Oncore design. Bob Q. ----- Original Message ----- From: "Patrick Reynaert" <preynaert@yahoo.com> To: "time-nuts" <time-nuts@febo.com> Sent: Sunday, December 21, 2008 2:13 PM Subject: [time-nuts] Jupiter modules: 1pps or 10kHz to lock an OCXO ? > Hello, > > > Using the 10kHz output to lock an OCXO is common practice and seems to > give good results. > > Has anyone tried to use the 1pps output? One? could first make a simple > divider to create a 0.5Hz reference with 50% duty cycle, and then use this > signal to lock an OCXO. This would also allow the use of other OEM GPS > modules that don't have the 10kHz but only the 1pps signal. > > Of course, as the 0.5Hz signal is much lower in frequency than 10kHz, the > short-term stability is pushed more to the OCXO, making the requirements > of the OCXO even harder. > > But maybe the 1pps signal has better stability than the 10kHz signal? Or > is this the same since these signals will only influence the long-term > stability of the oscillator and have the same accuracy? > > Any thoughts are highly appreciated. > > Thanks, > Patrick. > > > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.

If you are trying to have precise enough frequency for ham microwave applications for instance (1E-9 would be 10 Hz at 10 GHz), the 10kHz output of the Jupiter can be used to your advantage to phase lock a cheap VCXO with a short time constant. A perfect example is the Jim Miller design which Tom (and others) has tested and found to perform very well. A short time constant is advantageous because it means the system will phase lock quickly after power up, and many ham microwave stations are mobile and do not remain powered all the time. However, if you try to phase lock a relatively good OCXO like the HP 10811 or better (and achieve 1E-11 or better), any time constant faster than 20 minutes or so is likely to actually degrade the available performance of the OCXO because the GPS signal has a lot of fluctuations in the short term due to atmospheric perturbations and satellite position in the sky, refered to as geometry, so a fast loop will force the otherwise stable OCXO to follow the short term instability of the GPS signal, not what you want. With that kind of time constant, it makes little difference if the phase detector works at 10 kHz or 1Hz, aside from saving a few dividers. As it has been pointed out, long time constants are better implemented in software, due to the negative effect of large value resistors on noise. Tom has a lot of very useful charts on his site www.leapsecond.com showing the relative effects of GPS jitter and OCXO drift on overall stability. Conclusions: 1) if you have a Jupiter and your needs are modest, use the 10kHz and an analog loop, it will make your life easier (fewest parts), but depending on the reference oscillator you use and the performance you try to achieve, do not speed up the loop unnecessarily. 2) if you only need 1E-9 stability, the Jim Miller design is excellent and so simple, anything else would be a waste. 3) if you need 1E-11 or better, you will need much more hardware, including a good quality GPS receiver, antenna and OCXO and a microprocessor to implement the loop filter, and probably some holdover algorithms, essentially what you will find in a Fury, Z3801, Thunderbolt or Brandywine integrated GPSDO. 4) if your needs are in between, you have a lot of room for experimentation. Didier KO4BB > -----Original Message----- > From: time-nuts-bounces@febo.com > [mailto:time-nuts-bounces@febo.com] On Behalf Of Bob Q > Sent: Sunday, December 21, 2008 8:34 PM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] Jupiter modules: 1pps or 10kHz to > lock an OCXO ? > > I thought of something else. Time to lock can be really > long. Say the OCXO can swing +/- 1 ppm, +/- 10 Hz at 10 MHz. > The +/- 1 ppm also applies to 0.5 Hz. To swing 180 degrees > at 0.5 Hz, assuming the low pass filtered control signal > pushes the OCXO the full 1 ppm, will take 1e6 seconds unless > you use a circuit similar to what I used to prealign 50 Hz > signals in the 100 Hz Motorola Oncore design. > Bob Q. > ----- Original Message ----- > From: "Patrick Reynaert" <preynaert@yahoo.com> > To: "time-nuts" <time-nuts@febo.com> > Sent: Sunday, December 21, 2008 2:13 PM > Subject: [time-nuts] Jupiter modules: 1pps or 10kHz to lock an OCXO ? > > > > Hello, > > > > > > Using the 10kHz output to lock an OCXO is common practice > and seems to > > give good results. > > > > Has anyone tried to use the 1pps output? One? could first make a > > simple divider to create a 0.5Hz reference with 50% duty cycle, and > > then use this signal to lock an OCXO. This would also allow > the use of > > other OEM GPS modules that don't have the 10kHz but only > the 1pps signal. > > > > Of course, as the 0.5Hz signal is much lower in frequency > than 10kHz, > > the short-term stability is pushed more to the OCXO, making the > > requirements of the OCXO even harder. > > > > But maybe the 1pps signal has better stability than the > 10kHz signal? > > Or is this the same since these signals will only influence the > > long-term stability of the oscillator and have the same accuracy? > > > > Any thoughts are highly appreciated. > > > > Thanks, > > Patrick. > > > > > > > > > > > > _______________________________________________ > > time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com To unsubscribe, > go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.

I have one of the circular Trimbel units, I think it might be a Jupiter? Anyway, what I'm after is one of the multi-way plugs so that I can connect it up and start to use it. Does anyone know of a source for these plugs please? Thanks - Dave

Hi Dave, Farnell sell the plugs for the Pallisade (I assume you have the selfcontained antenna/receiver unit). You have to buy the plug houding and contacts separately. The manual (available online) has the part numbers if you look carefully). I'm in California at the moment so don't have easy access to give you full part numbers. I'f you can't identify the parts let me know.   Robert G8RPI. --- On Mon, 22/12/08, Dave Ackrill <dave.g0dja@tiscali.co.uk> wrote: From: Dave Ackrill <dave.g0dja@tiscali.co.uk> Subject: [time-nuts] Trimble multi-way socket To: "Discussion of precise time and frequency measurement" <time-nuts@febo.com> Date: Monday, 22 December, 2008, 1:57 PM I have one of the circular Trimbel units, I think it might be a Jupiter? Anyway, what I'm after is one of the multi-way plugs so that I can connect it up and start to use it. Does anyone know of a source for these plugs please? Thanks - Dave _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.

Robert Atkinson wrote: > Hi Dave, > Farnell sell the plugs for the Pallisade (I assume you have the selfcontained antenna/receiver unit). You have to buy the plug houding and contacts separately. The manual (available online) has the part numbers if you look carefully). I'm in California at the moment so don't have easy access to give you full part numbers. I'f you can't identify the parts let me know. > > Robert G8RPI. > Thanks Robert, Yes, it is the Pallisade in the white self contained unit. So, I'll hunt round in the Farnell catalogue. Thanks for the information. Cheers - Dave (G0DJA)

Robert Atkinson wrote: > Hi Dave, > Farnell sell the plugs for the Pallisade (I assume you have the selfcontained antenna/receiver unit). You have to buy the plug houding and contacts separately. The manual (available online) has the part numbers if you look carefully). I'm in California at the moment so don't have easy access to give you full part numbers. I'f you can't identify the parts let me know. > From the GM4ISM website at http://www.dc2light.pwp.blueyonder.co.uk/Webpage/GPS_ref.htm I discovered that I needed the "backshell, part no. 6810-204-2001 and sockets, part no. 6862-201-22278". However, although I've found the sockets (Deutsch 6862-201-22278 - look for the alternative RoHS compliant type) in Farnell, but I'm not so sure about the backshell. The information on the GM4IS page says I need a 6810-204-2001 but the list in the online catelogue only has 6810-201-2001, in various diameters, and a couple of 6810-204-1001, both 5.08mm diameter. So, I'm not sure which one would be correct. Does anyone have more information that would help please? Thanks - Dave